/* v4-toy: Circuit Playground (sections/circuit-toy.liquid).
   State lives in data-* on [data-toy]; every visual below is derived from it, so the
   server-rendered default (parallel, 1 cell, S1 closed) is correct without JS. */

.toy{--toy-paper:#ECE6DA;--toy-print:#2B261F;--toy-print-2:#6A6155;--toy-copper:#BC7135;--toy-copper-edge:#87471A;--toy-copper-hi:#EBB07A;--toy-ease:var(--ease-out,cubic-bezier(.16,1,.3,1))}

/* ---------- head ---------- */
.toy__head{display:grid;grid-template-columns:minmax(0,1.1fr) minmax(0,1fr);gap:clamp(24px,5vw,80px);align-items:end;margin-bottom:clamp(28px,4vw,48px)}
.toy__title{margin:0;font-size:clamp(2.5rem,5.6vw,5.25rem);line-height:.94;letter-spacing:-.04em;max-width:11ch;text-wrap:balance}
.toy__intro{max-width:44ch}
.toy__intro p{margin:0 0 10px;color:var(--ink-2);font-size:clamp(1.02rem,1.3vw,1.15rem);line-height:1.55}
.toy__link{color:var(--ink)}
.toy__link:hover{color:var(--orange-hi)}

/* ---------- bench layout ---------- */
.toy__bench{display:grid;grid-template-columns:minmax(0,1fr) minmax(320px,380px);gap:clamp(16px,2vw,24px);align-items:stretch}
.toy__mat{margin:0;position:relative;border:1px solid var(--line);border-radius:10px;background-color:var(--bg-sunk);
  background-image:linear-gradient(#ffffff08 1px,transparent 1px),linear-gradient(90deg,#ffffff08 1px,transparent 1px);
  background-size:32px 32px;background-position:-1px -1px;padding:clamp(10px,2vw,28px);display:flex;align-items:center;min-width:0}
.toy-svg{display:block;width:100%;height:auto;overflow:visible;font-family:var(--font-mono);-webkit-user-select:none;user-select:none}

/* ---------- card + print ---------- */
.toy-card{fill:var(--toy-paper);stroke:#00000022;stroke-width:1}
.toy-crop path{fill:none;stroke:#00000030;stroke-width:1.2}
.toy-print{font-size:13px;letter-spacing:.06em;fill:var(--toy-print-2)}
.toy-print--mode{font-size:15px;fill:var(--toy-print);letter-spacing:.08em}
.toy-label{font-size:17px;font-weight:600;letter-spacing:.04em;fill:var(--toy-print)}
.toy-label--sub{font-size:13.5px;font-weight:400;fill:var(--toy-print-2)}
.toy-label--m{display:none}

/* ---------- copper ---------- */
.toy-route{transition:opacity .28s var(--toy-ease)}
.toy-tape{fill:none;stroke:var(--toy-copper);stroke-width:18;stroke-linejoin:miter;stroke-linecap:butt}
.toy-tape-edge{fill:none;stroke:var(--toy-copper-edge);stroke-width:19.5;stroke-linejoin:miter;stroke-opacity:.55}
.toy-tape-sheen{fill:none;stroke:var(--toy-copper-hi);stroke-width:5;stroke-opacity:.32;stroke-linejoin:miter}
.toy-crease{fill:none;stroke:var(--toy-copper-edge);stroke-width:1.2;stroke-opacity:.6}
.toy-pad{fill:var(--toy-copper);stroke:var(--toy-copper-edge);stroke-width:1}
.toy-fold{fill:none;stroke:var(--toy-print-2);stroke-width:1;stroke-dasharray:3 4;opacity:.75}
[data-mode=parallel] .toy-route--series,[data-mode=series] .toy-route--parallel{opacity:0}
.toy-when-series,.toy-when-2cell,.toy-when-s1-open,.toy-when-s2-open{display:none}
[data-mode=series] .toy-when-series,[data-cells="2"] .toy-when-2cell,[data-s1=open] .toy-when-s1-open,[data-s2=open] .toy-when-s2-open{display:inline}
[data-mode=series] .toy-when-parallel,[data-cells="2"] .toy-when-1cell,[data-s1=open] .toy-when-s1-closed,[data-s2=open] .toy-when-s2-closed{display:none}

/* ---------- battery ---------- */
.toy-cell-rim{fill:none;stroke:#5E646D;stroke-width:1.2}
.toy-cell-ring{fill:none;stroke:#ffffff70;stroke-width:1}
.toy-engrave{font-size:12px;letter-spacing:.1em;fill:#5B616A}
.toy-engrave--plus{font-size:22px;font-weight:500}
.toy-flap{fill:#F2EDE3;stroke:#00000018;stroke-width:1}
.toy-cell2{opacity:0;transition:opacity .25s var(--toy-ease)}
[data-cells="2"] .toy-cell2{opacity:1}

/* ---------- switches ---------- */
.toy-tab{transition:transform .32s var(--toy-ease)}
.toy-tab-paper{fill:#F3EEE5;stroke:#00000020;stroke-width:1}
.toy-tab-paper--under{fill:#E6DFD2}
.toy-tab-copper{fill:var(--toy-copper);stroke:var(--toy-copper-edge);stroke-width:.8}
.toy-tab-notch{fill:none;stroke:#0000002a;stroke-width:1}
.toy-tab-under{opacity:0;transition:opacity 0s linear .16s}
.toy-tab-face{transition:opacity 0s linear .16s}
[data-s1=open] .toy-switch--1 .toy-tab,[data-s2=open] .toy-switch--2 .toy-tab{transform:scaleY(-1)}
[data-s1=open] .toy-switch--1 .toy-tab-under,[data-s2=open] .toy-switch--2 .toy-tab-under{opacity:1}
[data-s1=open] .toy-switch--1 .toy-tab-face,[data-s2=open] .toy-switch--2 .toy-tab-face{opacity:0}
.toy-svg *{pointer-events:none}
.toy-hit{fill:transparent;pointer-events:none}
.toy.is-ready .toy-hit{pointer-events:all}
.toy.is-ready .toy-hit{cursor:pointer}
.toy.is-ready .toy-switch:hover .toy-tab-paper{fill:#FBF7F0}

/* ---------- LEDs ---------- */
.toy-leg{fill:#C7CBD1;stroke:#7D838C;stroke-width:.7}
.toy-sellotape{fill:#ffffff40;stroke:#ffffff99;stroke-width:.8}
.toy-flange{fill:#6E1D14;stroke:#4A120C;stroke-width:1;transition:fill .2s var(--toy-ease)}
.toy-polarity{font-size:15px;font-weight:600;fill:var(--toy-print-2)}
.toy-spec{fill:#ffffff;opacity:.38}
.toy-glow,.toy-dome--on,.toy-halo{opacity:0;transition:opacity .22s var(--toy-ease)}
.toy-halo{fill:none;stroke:#FF7A00;stroke-width:6}

/* lit when its loop is closed (mirrors v4-toy.js: parallel = own switch; series = S1 + S2 + 6 V) */
[data-mode=parallel][data-s1=closed] .toy-led--1 :is(.toy-glow,.toy-dome--on),
[data-mode=parallel][data-s2=closed] .toy-led--2 :is(.toy-glow,.toy-dome--on),
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy-led :is(.toy-glow,.toy-dome--on){opacity:1}
[data-mode=parallel][data-s1=closed] .toy-led--1 .toy-halo,
[data-mode=parallel][data-s2=closed] .toy-led--2 .toy-halo,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy-led .toy-halo{opacity:.55}
[data-mode=parallel][data-s1=closed] .toy-led--1 .toy-flange,
[data-mode=parallel][data-s2=closed] .toy-led--2 .toy-flange,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy-led .toy-flange{fill:#D9531A}
[data-mode=parallel][data-s1=closed] .toy-led--1 .toy-spec,
[data-mode=parallel][data-s2=closed] .toy-led--2 .toy-spec,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy-led .toy-spec{opacity:.7}

/* ---------- current pulses ---------- */
.toy-pulse{fill:none;stroke:var(--orange);stroke-width:6;stroke-linecap:round;opacity:0;transition:opacity .2s var(--toy-ease)}
[data-mode=parallel][data-s1=closed] .toy-pulse--a,
[data-mode=parallel][data-s2=closed] .toy-pulse--b,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy-pulse--s{opacity:1}
@media (prefers-reduced-motion:no-preference){
  .toy-pulse{animation:toy-flow var(--toy-dur,10s) linear infinite}
  body.is-motion-paused .toy-pulse{animation-play-state:paused}
}
@keyframes toy-flow{to{stroke-dashoffset:-1}}

/* ---------- panel ---------- */
.toy__panel{display:flex;flex-direction:column;border:1px solid var(--line);border-radius:10px;background:var(--bg-raised);padding:4px 20px 20px;min-width:0}
.toy__group{padding:16px 0;border-bottom:1px solid var(--line)}
.toy__glabel{display:flex;justify-content:space-between;align-items:baseline;gap:12px;margin:0 0 10px;font-family:var(--font-mono);font-size:.75rem;letter-spacing:.04em;color:var(--ink-2)}
.toy__hint{color:var(--ink-3);font-size:.75rem}
.toy__seg{display:grid;grid-template-columns:1fr 1fr;gap:8px}
.toy__btn{appearance:none;display:flex;align-items:center;gap:10px;min-height:52px;padding:10px 14px;border:1px solid var(--line-2);border-radius:6px;background:transparent;color:var(--ink-2);font:inherit;font-size:.95rem;font-weight:600;text-align:left;cursor:pointer;transition:background-color .18s var(--toy-ease),border-color .18s var(--toy-ease),color .18s var(--toy-ease)}
.toy__btn:hover{background:var(--bg-hi);color:var(--ink);border-color:var(--ink-3)}
.toy__btn[aria-pressed=true]{background:var(--bg-hi);color:var(--ink);border-color:var(--ink-3)}
.toy__btn:focus-visible{outline:2px solid var(--orange);outline-offset:2px}
.toy__unit{margin-left:auto;font-family:var(--font-mono);font-size:.75rem;font-weight:400;letter-spacing:.04em;color:var(--ink-3)}
.toy__btn[aria-pressed=true] .toy__unit{color:var(--ink-2)}
.toy__lamp{flex:none;width:8px;height:8px;border-radius:50%;background:var(--line-2);box-shadow:inset 0 0 0 1px #ffffff10;transition:background-color .18s,box-shadow .18s}
.toy__btn[aria-pressed=true] .toy__lamp{background:var(--orange);box-shadow:0 0 10px 1px #FF7A0099}
.toy__sym{flex:none;width:40px;height:18px;overflow:visible}
.toy__sym circle{fill:var(--bg-raised);stroke:currentColor;stroke-width:1.6}
.toy__sym-wire{stroke:currentColor;stroke-width:1.6;fill:none}
.toy__sym-lever{stroke:currentColor;stroke-width:2;stroke-linecap:round;fill:none;transform-box:view-box;transform-origin:10px 14px;transform:rotate(-28deg);transition:transform .22s var(--toy-ease)}
.toy__btn[aria-pressed=true] .toy__sym-lever{transform:none}
.toy__state{margin-left:auto;font-family:var(--font-mono);font-size:.75rem;font-weight:400;letter-spacing:.04em;color:var(--ink-3)}
.toy__btn[aria-pressed=true] .toy__state{color:var(--ink-2)}
.toy__state-closed,.toy__btn[aria-pressed=true] .toy__state-open{display:none}
.toy__btn[aria-pressed=true] .toy__state-closed{display:inline}

.toy__readout{margin-top:16px;padding:16px;border-radius:6px;background:var(--bg-sunk);border:1px solid var(--line)}
.toy__leds{display:flex;gap:8px;margin-bottom:12px}
.toy__ind{display:inline-flex;align-items:center;gap:6px;padding:5px 10px 5px 8px;border:1px solid var(--line-2);border-radius:999px;font-family:var(--font-mono);font-size:.75rem;letter-spacing:.04em;color:var(--ink-3)}
.toy__ind::before{content:"";width:7px;height:7px;border-radius:50%;background:var(--line-2)}
.toy__ind b{font-weight:500}
.toy__ind-on{display:none}
[data-mode=parallel][data-s1=closed] .toy__ind--1,
[data-mode=parallel][data-s2=closed] .toy__ind--2,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy__ind{color:var(--ink);border-color:#FF7A0066}
[data-mode=parallel][data-s1=closed] .toy__ind--1::before,
[data-mode=parallel][data-s2=closed] .toy__ind--2::before,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy__ind::before{background:var(--orange);box-shadow:0 0 8px 1px #FF7A00aa}
[data-mode=parallel][data-s1=closed] .toy__ind--1 .toy__ind-on,
[data-mode=parallel][data-s2=closed] .toy__ind--2 .toy__ind-on,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy__ind .toy__ind-on{display:inline}
[data-mode=parallel][data-s1=closed] .toy__ind--1 .toy__ind-off,
[data-mode=parallel][data-s2=closed] .toy__ind--2 .toy__ind-off,
[data-mode=series][data-cells="2"][data-s1=closed][data-s2=closed] .toy__ind .toy__ind-off{display:none}
.toy__status{margin:0 0 6px;font-family:var(--font-mono);font-size:.75rem;letter-spacing:.04em;color:var(--ink-2)}
.toy__sentence{margin:0 0 10px;font-size:1.02rem;line-height:1.45;color:var(--ink);font-weight:500;text-wrap:pretty}
.toy__why{margin:0;font-size:.92rem;line-height:1.5;color:var(--ink-2);text-wrap:pretty}
.toy__why-k{font-family:var(--font-mono);font-size:.75rem;letter-spacing:.04em;color:var(--blue-text);margin-right:4px}
.toy__challenge{display:flex;align-items:baseline;gap:10px;margin:16px 0 0;font-size:.95rem;line-height:1.45;color:var(--ink-2)}
.toy__challenge .toy__lamp{transform:translateY(-1px)}
.toy__challenge.is-solved{color:var(--ink)}
.toy__challenge.is-solved .toy__lamp{background:var(--orange);box-shadow:0 0 10px 1px #FF7A0099}

/* ---------- responsive ---------- */
@media (max-width:1100px){
  .toy__bench{grid-template-columns:minmax(0,1fr)}
  .toy__panel{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));column-gap:20px}
  .toy__group{border-bottom:0}
  .toy__readout{grid-column:1/-1;margin-top:4px}
  .toy__challenge{grid-column:1/-1}
}
@media (max-width:800px){
  .toy__head{grid-template-columns:minmax(0,1fr);gap:16px}
  .toy__panel{grid-template-columns:minmax(0,1fr);padding:4px 16px 16px}
  .toy__group{border-bottom:1px solid var(--line)}
}
@media (max-width:600px){
  .toy__mat{margin-inline:-18px;padding:14px 6px;border-radius:0;border-inline:0;background-size:24px 24px}
  .toy__group{padding:14px 0}
  .toy__btn{min-height:48px}
  .toy-l2,.toy-print{display:none}
  .toy-label{font-size:30px}
  .toy-label--m{display:inline;font-size:26px;transform:translateY(16px)}
  .toy__btn{padding:10px 12px;font-size:.92rem}
  .toy__sym{width:34px}
}

/* ---------- motion off: instant state changes, no pulse animation ---------- */
@media (prefers-reduced-motion:reduce){
  .toy *,.toy *::before{transition:none!important;animation:none!important}
}
body.is-motion-paused .toy *{transition-duration:0s!important;transition-delay:0s!important}